Rule 1 of the Book of Laws of the Kingdom of Angels

Aurora is a student of Fine Arts who is protected by an angel called Ethan, but she doesn't know it. The Devil is threatening the Angels Kingdom's peace and, in consequence, human lives; so Ethan has to go to Earth and protect Aurora personally, as she owns something very important that can't be in Devil's hands. But love will complicate things and, in consequence, Ethan's mission.